Here is how you figure the cost. Take Volts x Amps = Watts. Watts x 1000 = kilowatts/Kilowatts x running hours = kilowatt hours. Kilowatt hours x your local rate = cost. Call your electric company and get the rate. As an example a 1/2HP draws 5 amps @115 volts at start up, and running amps are about 60% of that. Start up pulls more power and when you get it running it drops to 60%

jeff